Process for coloring aluminum and aluminum alloys

ABSTRACT

A process for coloring aluminum or aluminum alloy products which comprises anodically oxidizing a membrane of aluminum or an aluminum alloy in a solution containing a phosphorous oxide acid or an acid mixture of a phosphorous oxide acid and a second acid and treating said membrane with an aqueous pigment dispersion to adsorb the pigment onto the porous surface of the membrane.

United States Patent [191 Matsuo et a1,

[ 1 Oct. 29, 1974 PROCESS FOR COLORIING ALUMINUM AND ALUMINUM ALLOYSlnventors: Hiroto Matsuo; Tadamitsu Nakarnura, both of Saitama-ken,Japan Assignee: Dainichiseilta Color & Chemicals Mtg. Co., Ltd Tokyo,Japan Filed: Nov. 29, 1972 Appl. No: 310,442

Foreign Application Priority Data Dec. 24, 1972 Japan 47-104669 11.5.C1. 204/35 N, 204/38 A, 204/38 E, 204/58, 117/49, 148/61 lnt, Cl. C231)9/02, C23f 17/00 Field of Search 204/38 A, 35 N, 56 R, 58; 117/75, 49;148/61 References Cited UNITED STATES PATENTS 3/1955 Hesch 204/5810/1955 Axtell 204/38 A 1/1959 Weegaretal :.,.204/38A 3/1971 Hovey..204/38-E 3,594,289 7/1971 Watkinson et a1 204/38 A 3,622,473 11/1971Ohta et a1. 204/38 A 3,671,333 6/1972 Mosier 204/58 3,707,394 12/1972Clementson et al. 204/58 3,714,001 1/1973 Dorsey 204/38 A OTHERPUBLICATlONS Practical Implications of Research on Anodic Coatings on Alby J F. Murphy, Plating, November 1967, page 1,242.

Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 8, 2nd Ed., 1965,page 31.

Primary ExaminerJohn I'll. Mack Assistant ExaminerR. L. AndrewsAttorney, Agent, or Firm0blon, Fisher, Spivak, McClelland & Maier [5 7]ABSTRACT 13 Claims, No Drawings PROCESS FOR COLORING ALUMINUM ANDALUMINUM ALLOYS BACKGROUND OF THE INVENTION 1. Field Of The Invention:

This invention relates to a process for coloring aluminum and aluminumalloys. More particularly, it relates to a process for preparing pigmentcolored aluminum products possessing special varicolored characteristicsand having high fastness for. both indoor and outdoor applications.

2. Description Of The Prior Art:

The following processes for coloring aluminum or aluminum alloys arewell known:

I. A process for coloring aluminum or aluminum alloys which involves aninitial anodic oxidation step followed by the process of dipping theoxidized metal in a solution of a water-soluble or oil-soluble dye(Japanese Pat. No. 65742).

2. A process for coloring aluminum metals which involves the procedureof anodic oxidation, dipping the metal in an aqueous solution containinga metal salt, and electrolyzing the product with an alternating currentto color the metal with an inorganic material (Japanese Pat.Publications 1715/1963 and l6566/l97l).

4. A process for coloring aluminum metals by an electrolytic coloring ornatural coloring process in which a colored membrane is formed by asynergistic effect between a specific aluminum alloy and an electrolyticsolution when the metal is anodically oxidized (Japanese Pat.Publication No. 21284/1971).

The principal disadvantage of the products manufactured by process (I)is that the light fastness of the products is very low. Thus, theseproducts are difficult to use in outdoor applications where high lightfastness is required. Processes (2) and (3) are complicated-by the factthat the preparation of the electrolyte and the control of theelectrolytic conditions are difficult, and that the uniform coloring ofthe metal is difficult and the types of color which may be used arelimited. Process (4) has the disadvantages that a specifically prepared,high cost aluminum alloy is required in order to provide a uniformcolor, and the types of color which may be used are limited.

Several processes have been developed which are improvements over theolder processes, and they are outlined as follows:

5. A process for coloring aluminum metals in which a metal is treatedwith a concentrated sulfuric acid solution containing an organic pigmentwhich has a higher fastness than the previous dyes employed (JapanesePat. Publication No. 22843/1971). The organic' pigment may be applied tothe metal as a coating of paint. This process suffers from thedisadvantage that 98% sulfuric acid poses serious operational hazards aswell as being difficult to use. If the pigment is used in a paint, thecoating applied to the surface of a metal sometimes possesses inferioradhesiveness, transparency and clearness.

6. A process for coloring aluminum metal in which the surface pores ofan anodically oxidized membrane of aluminum are filled with a fineinorganic pigment in an electrophoresis process. The treated membrane issubsequently heated at 350C. to yield a product having a high scratchresistance and color (Japanese Pat. Publication No. l4038/ I968).

Process (6) has the advantage that there are no limitations on the typesof acids, dispersing agents, and inorganic pigments used in the anodicoxidation process. However, it has been found that it is impossible toimpregnate pigment particles into the pores of an anodically oxidizedmembrane and to adsorb pigment particles on the surface of the membrane.(the surface of which is formed by treatment with sulfuric acid, oxalicacid, chromic acid or a flame-injection method) because the activity ofthe surface and the size of the holes of the anodically oxidizedmembrane are changed by the conditions of the treatment. Aluminum metalstreated by conventional techniques have surfaces of low activity andhave pores on the surfaces which are very small. Moreover, thedispersing agents used to disperse the pigments in waterare veryimportant factors. When anionic, cationic and nonionic-anionicdispersing agents are employed, the pigment dispersion coagulatesrendering it inadequate for coloring aluminum.

A need therefore exists for a process of coloring aluminum and aluminumalloys which imparts beautiful colors of the metal while maintaining anexcellent degree of fastness.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide a process for coloring aluminum and aluminum alloys to formproducts which have a beautiful color and excellent color fastness.

This object and other objects of this invention, as hereinafter willbecome apparent, are achieved by the anodic oxidation of aluminum andaluminum alloys in the presence of an acid or mixture of acids derivedfrom a phosphorus oxide to form porous anodically oxidized membraneswhich are treated with an aqueous pigment dispersion. In order toovercome the disadvantages of the highly exothermic reaction of theprocess and the requirement for high bath voltages, an acid mixture ofan acid derived from a phosphorus oxide and an organic or an inorganicacid is preferably used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS obtained when said membranesare treated with an acid mixture of an acid derived from a phosphorousoxide such as phosphoric acid and another acid such as sulfuric acid.However, light colors are difficult to obtain on thick membranes whenonly an acid derived from a phosphorous oxide is used.

The aluminum and aluminum alloys of this invention have various shapes.Suitable aluminum alloys include alloys containing copper, silicon,iron, manganese, magnesium, zinc, chromium, titanium, lead, nickel orbismuth such as aluminum alloys 15, 25, 38, SA, 45, 525, 565, NP 5/6, A548, 618, 635, 148, A I78, I75, 24 S, 755 and the like. Hereinafter, theuse of the term aluminum will include aluminum alloys.

The following list outlines the test applied to aluminum and aluminumalloys:-

1 S [A 1050] 99.5071 Al normal 2 S v [A H] 99.00% Al do.

3 S [A 3003] Al-Mn alloy corrosion resistant! 150 SA [A 5005] Al-Mgallo) do.

4 S [A 3004] Al-Mg alloy do.

52 S [A 5052] Al-Mg allo corrosion resistant high strength 56 S [A 5056]AlMg alloy do.

NP 5/6 [A 5083] Al-Mg alloy do.

A 54 S [A 5l54] Al-Mg alloy do.

6l S [A 6061] Al-Mg-Si alloy corrosion resistant heat treated 63 S [A6063] Al-Mg-Si alloy do.

l4 S [A 2014] Al-Cu alloy Heat treated high strength A 17 S [2| l7]Al-Cu alloy do.

17 S [A 2017] Al-Cu alloy do.

24 S [A 2024] Al-Cu (plied) do.

75 S [A 7075] Al-Cu (plied) do.

The porous, anodically oxidized membranes of aluminum possess many finepin holes which are formed by passing an electric current of a specificdensity through the membrane in an acidic aqueous solution containing anacid or an acid mixture derived from phosphorus oxides. Suitable acidsderived from phosphorus oxides include orthophosphoric acid,metaphosphoric acid, pyrophosphoric acid, polymetaphosphoric acid andmixtures thereof. Orthosphosphoric acid, which is produced by adding P 0to water, is preferably used. Suitable organic and inorganic acids usedin the acid mixture include sulfuric acid, chromic acid, boric acid,oxalic acid, sulfamic acid, malonic acid, sulfosalicylic acid, maleicacid, citric acid, tartaric acid, phthalic acid, benzenesulfonic acid,succinic acid and lactic acid. Sulfuric acid and oxalic acid areespecially preferred.

The acids derived from phosphorus oxide and acid mixtures thereof areused in aqueous solutions at concentrations of ().l 30% by weight,preferably 2 by weight. When a mixture of acids is used, from 50 to l50weight percent of an inorganic acid or an organic acid is preferablyused based on the amount of phosphorous oxide derived acid used. Variousmetal salts such as aluminum sulfate may be added to the acid in orderto improve the stability of the bath and the anticorrosive properties ofthe anodically oxidized membranes. The conditions employed in the anodicoxidation of the aluminum metals include a bath temperature of 15 35C.,a reaction time of 10 60 minutes and a current density of 0.5 2.0 A/dmThe process of this invention may be modified by using a two-stepprocess in which the metal is anodically oxidized first in the presenceof an acid derived from phosphorous oxides and then is anodicallyoxidized again in the presence of an acid such as oxalic acid orsulfuric acid. Control of the anodic oxidation bath is rendered easierby this procedure than when the oxidation is conducted in the presenceof the acid mixture. The anodic oxidation step can be conducted in anacidic bath containing a pigment dispersion in such a manner that allowsthe pigment to adsorb on the anodically oxidized membrane. This latterprocedure has its advantages. However, the pigment used must be stableto acids and the oxidation conditions.

If the time lapse between the anodic oxidation of the membrane and itstreatment with an aqueous pigment dispersion is too long, the membranewill corrode and lose its activity. Therefore, it is preferable to sealthe surface of the membrane by treatment with steam or the like. Becausethe membranes are anodically oxidized in the presence of at least oneacid derived from phosphorous oxides, they maintain their ability toabsorb pigment from the aqueous pigment dispersion. On the other hand,if the membranes are anodically oxidized without the presence of an acidderived from a phosphorous oxide, the adsorbing capability of themembrane is quickly lost. By the process of this invention, the oxidizedmembranes normally retain their adsorbing capability for about two days,and, thus, should be treated within that period. The sealing treatmentcan be conducted by applying steam, hot water, nickel acetate, potassiumbichromate,'sodium silicate and the like to the oxidized membranes.

When an acid mixture is used in the anodic oxidation process, theadsorption capability of the oxidized membranes can be adjusted bychanging the ratio of the acid derived from a phosphorous oxide and theinorganic acid or the organic acid. The depth of color of the finishedproduct is also affected by the acid ratio. Proportionately greateramounts of the acids derived from phosphorous oxide increase the depthof the finished product. If the color depth attained is insufficientbecause of the conditions selected for the concentration of the acidmixture, the concentration of the aqueous pigment dispersion and thetype of pigment and the like, greater color depth may be achieved bypassing an electric current in the aqueous pigment dispersion bath as anauxiliary means for adsorption, i.e., electrophoresis. if theelectrophoresis technique is employed, a dispersing agent must be usedin the aqueous pigment dispersion bath. If has been found that aqueouspigment dispersions coagulate in the presence of anionic, cationic, ornonionic-anionic dispersing agents, but do not coagulate in the presenceof nonionic or nonioniccationic dispersing agents when used in anelectrolytic medium. Moreover, the nonionic or nonionic-cationicdispersing agents promote the adsorption of the pigment. If noelectrophoresis technique is employed, the type of dispersing agent usedis not limited.

It has been found'that the fastness of the colored aluminum productswith respect to weather durability, chemical resistance and the like canbe increased by coating the products with a suitable coating material,such as a resin.

The aqueous pigment dispersion can be prepared by dispersing a water andoil insoluble pigment with a nonionic, anionic or cationic dispersingagent. In the preparation of the dispersions, suitable pigments includeknown organic and inorganic pigment derivatives such as phthalocyanines,anthraquinones, perynones, perylenes, indigos, thioindigos, dioxadines,quinacridones, azo-coupled derivatives, azocondensation derivatives,isoindolenones, aniline black, carbon black, titanium oxide, chromeyellow, molybdenum red, iron oxide, chromium oxide green, cadmiumyellow, cadmium red, cobalt blue, barium sulfate, transparent ironoxide, etc., and mixtures thereof.

The dispersing agents can be known nonionic, anionic and cationicdispersing agents. Suitable nonionic dispersing agents includepolyethyleneglycol derivatives such as polyethyleneglycol-alkyl esters,-alkyl ethers, -alkylphenyl ethers, alkylamides; and polyalcohol partialesters such as oxyethyl-oxypropyl block copolymers, and sorbitanealiphatic acid esters. Suitable anionic dispersing agents includeammonium salts, amine salts and alkali metal salts of aliphatichydrocarbons, alkyl sulfonates, sulfuric acid esters such as sulfuricoil, alkyl sulfonates, arylsulfonates and carboxylic acidpolymers,alkylphosphonates, alkylphosphoric esters, and the like.Suitable cationic dispersing agents include alkylamine ethyleneoxidederivatives such as polyoxyethylenestearylamine, polyoxyethyleneoleylamine, polyoxyethylenelaurylamine and the like.

In order to disperse the pigment in the aqueous medium in the presenceofa dispersing agent, the pigment is crushed in a speed line mill, asand mill, a ball mill, a roller or an atomizing ultrasonic vibrator.The pigment in the resulting dispersion usually has a diameter less than5,u, preferably 0.0] 0.5,u.. The amount of pigment incorporated in thedispersion varies depending upon the type of inorganic pigment ororganic pigment used. Usually, the quantity of pigment employed rangesfrom 5 70 weight percent, preferably 50 weight percent. The amount ofdispersing agent used ranges from 1 500 weight percent, preferably 1 200weight percent, based on the amount of pigment. Protective colloids suchas methylcellulose, polyvinylalcohol and the like may also be added tothe dispersion.

The dispersion medium consists mainly of water. If necessary, an organicmedium miscible with water can be added. Suitable media include ketonessuch as acetone and methylethylketone; diols such as ethyleneglycol;triols such as glycerine; and cellosolves such as methylcellosolve.

When the aqueous pigment dispersion is applied to the porous anodicallyoxidized membrane, the concentration of pigment varies depending uponthe required depth of color, but is preferably in the range of 0.2 30%.The dispersion is prepared by diluting a concentrated dispersion from 11,000 times with deionized water. The methods employed for applying thedispersions to the anodically oxidized aluminum include dipping methods,spraying methods, flow coating methods, roller coating methods, andbrush coating methods.

Preferably, dip coating methods are used. The dip coating method isaccomplished by submerging the anodically oxidized aluminum in anaqueous pigment dispersion with a pH of less than 1 l, preferably lessthan 8, at 0C. 100C, preferably l0C. 70C., for more than i minute,preferably more than 3 minutes. In order to promote the adsorption ofthe pigment, it is possible to pass an electric current through thedispersion at 0C. 80C., preferably C. 40C., for 10 seconds to 10minutes, preferably 30 seconds to l minute. After the adsorption ofpigment, the product is treated with steam to seal the pinholes or iscoated with a coating composition. The coating composition can beprepared by dissolving a resin in water or another solvent. Suitableresin derivatives include acryls, alkyds,

melamines, acrylalkyds, ureas, vinyls and epoxys. The coatingcompositions can be applied to the colored aluminum products bysubmersion, spray coating, electrophoresis coating, roller coating andsimilar techniques.

a clear color, a transparent appearance, and the pigments do notseparate from the surface of the metal. In comparison with conventionalmethods which use organic pigments dissolved in concentrated sulfuricacid (see process (5) discussed in the prior art), the coloring processof this invention is very easy. It is also possible to use inorganicpigments which are insoluble in sulfuric acid, and organic pigments,which deteriorate in sulfuric acid, in this invention. Thus, aluminumproducts with many colors can be prepared.

in accordance with this invention, it is either unnecessary to pass anelectric current through the pigment dispersion or at most, an electriccurrent may be required for only a short time. Thus, coagulation of thepigment and deterioration of the anodically oxidized membranes are notfound.

Heretofore, it has been thought that pigments have a low affinity forbases, especially metal bases. However, unexpectedly, the results ofthis invention have shown that the dispersed pigments have a highaffinity for the surfaces of porous, oxidized membranes.

in the process of this invention, it is not necessary to pass anelectric current through the dispersion. However, the passage of anelectric current promotes the absorption of the pigment whose adsorptiondepends upon the conditions of the anodically oxidized membrane', theaqueous pigment dispersion and the type of pigment.

The colored product can be used without a coating. However, the coatingsof this invention impart greater weather durability, and chemicalresistance, in addition to promoting greater alkali resistance, and acidresistance and other fastness properties.

In conventional products prepared by an electrodeposition method and acoating method, the pigment is contained within the resin of a coatedfilm. This results in a product which possesses poor adhesibility of thepigment as well as a poorly transparent coating. If the coated film ismarred or peels through deterioration of the resins, the pigment isremoved with the coated film and exposes a noncolored metal surface. Inthis invention, however, even though the coated film may be peeled, thepigment is not removed and the metal surface is not exposed.Accordingly, repairs of the coated films are easily made. In thisinvention, the aqueous pigment dispersion and the coating compositioncan be separately applied so that total control of the process is verysimple. Thus, the colored products prepared in this manner, have a firstlayer of pigment particles adsorbed on the aluminum or the aluminumalloy and a second layer of a coated resinous film.

Having generally described the invention, a more complete understandingcan be obtained by reference tocertain specific Examples. In thefollowing Examples, the term part and percent, respectively, designatepart by weight and percent by weight.

EXAMPLE I A 52 S Aluminum plate having a length of 80 mm., a width ofmm. and a thickness of 1 mm., which acted as an anode, was dipped in anaqueous 4% phosphoric acid solution, and was anodically oxidized at thecurrent density of 1.0 A/dm at 30C. for minutes.

An aqueous, red pigment dispersion was prepared by stirring a mixture of20 parts of perylene red (CI Vat Red 29), 8.0 parts ofpolyoxyethylenestearylamine Condition of anodic oxidation Coloring Depthof condition Color Time of anodic Thickness of oxidized Dip time inoxidation membrane the dispersion minutes) (u) (minutes) 0 I20 colorless30 3 5 pale 30 3 l0 medium 60 7 30 deep EXAMPLE 2 A 63 S Aluminum platehaving a length of 100 mm., a width of 50 mm., and a thickness of 2 mm.was dipped in an aqueous 10% phosphoric acid solution and was anodicallyoxidized with adirect current at a current density of 2.0 A/dm at roomtemperature for 40 minutes.

An aqueous, black pigment dispersion was prepared by stirring a mixture.of parts of a channel type carbon black, 5 parts of sodium aliphaticcarbonate, and

75 parts of water in a speed line mill. A diluted, aqueous blackpigmentdispersion was prepared by mixing 100 parts of the concentrated blackpigment dispersion with 900 parts of deionized water. The anodicallyoxidized plate was washed with water, dipped in the diluted dispersionfor 10 minutes and washed with water. Then, the plate was treated withhot water to seal the pores ofthe surface. The resulting black coloredaluminum alloy had a high light fastness.

EXAMPLE 3 A Aluminum plate having a length of 100 mm., a width of 50mm., and a thickness of l mm. was dipped in an aqueous 8% phosphoricacid solution and was anodically oxidized with a DC current at thecurrent density of L0 A/dm'- at 28C. for 30 minutes.

An aqueous blue pigment dispersion was prepared by stirring a mixture of50.9 parts of copper phthalocyanine paste (39.3% solid content), 8 partsof polyoxyethylene nonylphenyl ether (HLB 14.2) and 41.] parts water ina speed line mill. A diluted, aqueous blue pigment dispersion having apH of 5 was prepared by mixing 200 parts of the concentrated bl u edispe riQn,with 800 parts of deionized water and with formic acid. Theanodically oxidized plate was washed with water and dipped in thedispersion for 5 minutes. A direct current having a density of 20 mA/dmwas passed between the oxidized plate acting as an anode and a stainlesssteel cathode plate having a length of mm., a width of 50 mm., and athickness of 1 mm. at room temperature for 30 minutes. The resultingcolored plate was washed, and treated with hot water to seal the pinlikepores in accordance with the process of Example 2, to yield a bluecolored aluminum alloy plate characterized by a clear transparentuniform color with a high light fast- EXAMPLE 4 In this Example, theblue colored aluminum alloy plate produced by the procedure of Example3, was treated in a l5% aqueous solution of a water soluble acryl resinWater sol S-7 l0 manufactured by Dainippon Ink Co. by passing a directcurrent at volts at a bath temperature of 25C. for 3 minutes betweensaid plate acting as an anode and a stainless steel plate acting as acathode in accordance with the procedure of Example 3, instead ofsealing the surface of the plate. The resulting plate was washed withwater and cured by heating to yield a blue colored aluminum alloy platehaving a uniform color and lubrication. The thickness of the membranewas 2111. as determined by permascopic measurement.

To show the effectiveness of this procedure over the procedures of theprior art, an anodically oxidized reference aluminum alloy plate wascoated with the pigment and the water soluble acrylic resin. Theproperties of the coated film of the reference plate were similar tothose of the plate of the example. However, when the coated films onboth plates were removed, the appearance of the reference plate waspoor, but the ap- 5 pearance of the former plate was not altered becauseof its colored base. The film properties of the plates are compared asshown in Table l.

T KELET Properties Test method Test result anodic oxldatlon anodicoxidation EXAMPLE persion having a pH of 7.3 was prepared by mixing 200parts of the concentrated dispersion with 800 parts of deionized water.

The anodically oxidized plate was washed with water, dipped in thedispersion for 30 minutes, and washed with water to yield a greencolored aluminum alloy plate. The depth of color was varied as indicatedin Table 11.

EXAMPLE An aqueous, blue pigment dispersion was prepared by stirring50.9 parts (39.3% solid content) of copper phthalocyanine blue paste, 8parts of polyoxye- 5 thylenenonylphenylether (HLB 14.2) and 41.1 partsof water in a speed line mill. 300 Parts of the concentrated dispersionwere admixed with 700 parts of deionized water and the diluted aqueousblue pigment was sprayed on the anodically oxidized aluminum alloy ofExample 1 for minutes. The alloy was washed with water, dried in air,and then dipped in a trichlene solution of an acryl resin heated at 70C.for seconds.

The alloy was cured to yield a clear, deep blue colored aluminum alioyplate.

EXAMPLE 16 A coloring, bath was prepared by mixing 100 parts of theaqueous pigment dispersion of TABLE 11 Condition of anodic oxidationColoring Depth of condition color Time for anodic Membrane Dip time inoxidation (min.) thickness (;L) disperesion (min.)

0 0 120 colorless 15 3.5 10 pale 15 3.5 30 pale-medium 3O 7 30 medium 307 60 deep EXAMPLES 6 14 in the following Examples, the anodic oxidationbath of Example 5 was employed. The aluminum alloy plates wereanodically oxidized at a current density of 1.0 A/dm at 28C. for 50minutes and then were dipped in the aqueous green pigment dispersion ofExample 5 for 5 minutes. The voltage, membrane thickness, and

depth of color were varied depending upon the bath ska'aai'iqnd 9T0 aasarairaqtezr 10% "p565 phoric acid solution. A degreased 25 Aluminumplate having a length of 100 mm., a width of mm., and a I thickness of lmm. was dipped in the bath and was vanodically oxidized by passing adirect current at a density of 1.0 A/dm at 28C. for 40 minutes. Theplate was washed with water and treated with hot water to seal the poresto yield a clear, red colored aluminum alloy conditions as shown inTable 111. a plate.

TABLE 111 Example Bath Voltage Membrane Depth of Thickness Color 6phosphoric sulfuric acid (10%) acid (10%) 18 7.0 medium 7 do. malonicacid (571) 7.5 deep 8 do. sulfamic n a do. acid (17) A 68 6 deep 9 do.boric acid (3%) 80 9 medium 10 do. citric acid (1%) 6 medium 1 I do.citric acid (3'71) 7- medium 12 do. +oxalic I acid (1%) 68 7.5 deep 13do. oxalic acid (2%) 75 10.0 deep 14 do. (3%) oxalic acid (7%) 45 14deep sulfuric acid (067:) Ref.

1 phosphoric acid (10%) 75 7.5 deep 7 r 2 do. (159?) 58 3.5 deep EXAMPLE17 A degreased 2S aluminum plate having a length of 10 mm., a width of50 mm., and a thickness of 1 mm. was dipped in an aqueous l/( phosphoricacid solution 12 2. The process of claim 1, wherein an electric currentis passed through the aqueous pigment dispersion.

3. The process of claim 1, wherein the porous anodi cally oxidizedmembrane is treated with the aqueous brane with an aqueous pigmentdispersion consisting essentially of water, a pigment and a dispersingagent, whereby the pigment is impregnated into the porous surface of themembrane.

and was anodically oxidized at a current density of 1.0 pigmentdispersion .then A/dm (70 Volt) at 28C. for 30 minutes. The plate was ofi .Wherem i membrtne washed with water and then further anodicallyoxidized lmpregrtited with pigment is Coated a coatmg in an aqueous 15%sulfuric acid solution at 25C. with Composmon' a direct current at aconstant voltage of 12 volts. The The procfess of Claim wherem theanodlc k inmal Current density applied was 5 m -z and it tion process lSconducted together with the adsorption was increased to 100 m A/dm2after minutgs to l of the pigment in said acid solution containing saidpig- A/dm after minutes, and maintained at l A/dm for mem dlsperslon' anadditional 10 minutes to yield the anodically oxiprocess of claim 1 mga-amm m wfi g f ggl'l f gg g l g fi g g gf gg 15 alloy IS an alloy ofaluminum and another metal sethe (I uegus dispersin .1 lected from thegroup consisting of copper, silicon,

pg p y d iron, manganese magnesium, zinc, chromium, titagreen coloredaluminum alloy plate. The depth of color ium lead nickel bismuth andmixtures thereof and thickness of the anodically oxidized membrane f Vflrwwwflgkmw were altered by varying the oxidation conditions as I hePFOCCSS 0f Claim Where! Said PhOSPhOFOUS shown in Table IV. 20 oxideacid is selected from the group consisting of or- TABLE IV ColoringDepth of Condition of anodic oxidation condition color Total Dip Time inPrimary anodic Secondary anodic thickness dispersion oxidation oxidation(I571 H2504) of mem- (10% HGPOJ) time (min) brane (i min.) TimeThickness (min.) (1

I0 2.5 9 6 pale 10 2.5 do. 9 medium 20 4.5 do. 1 l 6 pale-medium 20 4.5do. ll 30 dee 30 7.0 do. 13 6 e ium 30 7.0 do I3 30 deep 30 7.0 7 6 deep.When sulfuric acid was replaced with oxalic acid, simithop h o s phoric5681"rheiaphdiiifi"iiiTfiyfbfiEi's-' lar results were obtained. 40phoric acid and polymetaphosphoric acid.

EXAMPLE l8 8. The process of claim 1, wherein said second acid in saidacid mixture is selected from the group consist- The anodically oxidizedaluminum plate of Example ing of sulfuric acid, chromic acid, boricacid, oxalic l was treated with hot water to seal the pores, and thenacid, sulfamic acid, malonic acid, sulfosalicylic acid, was dipped inthe aqueous pigment dispersion of Exammaleic acid, citric acid, tartaricacid, phthalic acid, ple l to yield a clear, red colored aluminum alloy.benzenesulfonic acid, succinic acid, lactic acid or mix- Having nowfully described the invention, it will be tures thereof. apparent to oneof ordinary skill in the art that many I e We changes and modificationscan be made thereto with- The-process Of-cldl,m wherem h congemmuo-n ofthe pigment having an average particle diameter in out departing fromthe spirit or scope of the invention 5 h f0 01 3 0 v l f, H f l as Setforth herein t elrange o f 2;; "3611750 ution o a p rom Accordingly,what is claimed as new and intended to a a B g O be covered by LettersPat nt is; 10. The process of claim 1, wherein said aqueous pigl. Aprocess for coloring aluminum and aluminum mem SPrSl0n 8 applied by adlp method. y )Vhlch QWR llt The process of claim 1 wherein said aqueouspiganodically oxidizing a membrane of aluminum or an mem dispersion isapplied by a spray h d allimlllwm alloy at temPerawre of from 15 12. Acolored aluminum or aluminum alloy product 35 11 Solutlon comamlng Q bproduced by a process, which-comprises the steps of: y g gffigffzmg gfaifggg g"a; anodically oxidizing a membrane of aluminum or an 9 8 b p fd b. d th aluminum alloy at a temperature of from 15 C y welg t 0 Ase on35C in a solution containing from 0.1 30% by amount of phosphorous oxideacid used, wherein ....s. s. .z the total concentration of said acidmixture ranges weight of a Phosphorous Oxide a cld or an and from O. l30% by weight and treating said memture of a Phosphorous Oxlde acld andfrom 50 to by weight of a second acid based on the amount of phosphorousoxide acid used, wherein the total concentration of said acid mixtureranges from 0.] 30% by weight and treating said meml3 l4 brane with anaqueous pigment dispersion consistporous surface of the membrane.

ing essentially of water, pigment and a dispersing 13. The coloredaluminum or aluminum alloy prodagent, whereby the pigment is impregnatedinto the uct of claim 12 which is coated with a layer of resin.

1. A PROCESS FOR COLORING ALUMINUM AND ALUMINUM ALLOYS, WHICH COMPRISES:ANODICALLY OXIDIZING A MEMBRANE OF ALUMINUM OR AN ALUMINUM ALLOY AT ATEMPERATURE OF FROM 15* - 35*C IN A SOLUTION CONTAINING FROM 0.1 - 30%BY WEIGHT OF A PHOSPHOROUS OXIDE ACID OR AN ACID MIXTURE OF APHOSPHOROUS OXIDE ACID AND FROM 50 TO 150% BY WEIGHT OF A SECOND ACIDBASED ON THE AMOUNT OF PHOSPHOROUS OXIDE ACID USED, WHEREIN THE TOTALCONCENTRATION OF SAID ACID MIXTURE RANGES FROM 0.1 - 30% BY WEIGHT ANDTREATING SAID MEMBRANE WITH AN AQUEOUS PIGMENT DISPERSION CONSISTINGESSENTIALLY OF WATER, A PIGMENT AND A DISPERSING AGENT, WHEREBY THEPIGMENT IS IMPREGNATED INTO THE POROUS SURFACE OF THE MEMBRANE.
 2. Theprocess of claim 1, wherein an electric current is passed through theaqueous pigment dispersion.
 3. The process of claim 1, wherein theporous anodically oxidized membrane is treated with the aqueous pigmentdispersion and then sealed.
 4. The pRocess of claim 1, wherein saidmembrane impregnated with a pigment is coated with a coatingcomposition.
 5. The process of claim 1, wherein the anodic oxidationprocess is conducted together with the adsorption of the pigment in saidacid solution containing said pigment dispersion.
 6. The process ofclaim 1, wherein said aluminum alloy is an alloy of aluminum and anothermetal selected from the group consisting of copper, silicon, iron,manganese, magnesium, zinc, chromium, titanium, lead, nickel, bismuthand mixtures thereof.
 7. The process of claim 1, wherein saidphosphorous oxide acid is selected from the group consisting oforthophosphoric acid, metaphosphoric acid, pyrophosphoric acid andpolymetaphosphoric acid.
 8. The process of claim 1, wherein said secondacid in said acid mixture is selected from the group consisting ofsulfuric acid, chromic acid, boric acid, oxalic acid, sulfamic acid,malonic acid, sulfosalicylic acid, maleic acid, citric acid, tartaricacid, phthalic acid, benzenesulfonic acid, succinic acid, lactic acid ormixtures thereof.
 9. The process of claim 1, wherein the concentrationof the pigment having an average particle diameter in the range of0.01 - 3.0 Mu in a solution of a pH from 1 - 11 is in a range of 0.2 -30%.
 10. The process of claim 1, wherein said aqueous pigment dispersionis applied by a dip method.
 11. The process of claim 1, wherein saidaqueous pigment dispersion is applied by a spray method.
 12. A coloredaluminum or aluminum alloy product produced by a process, whichcomprises the steps of: anodically oxidizing a membrane of aluminum oran aluminum alloy at a temperature of from 15* - 35*C in a solutioncontaining from 0.1 - 30% by weight of a phosphorous oxide acid or anacid mixture of a phosphorous oxide acid and from 50 to 150% by weightof a second acid based on the amount of phosphorous oxide acid used,wherein the total concentration of said acid mixture ranges from 0.1 -30% by weight and treating said membrane with an aqueous pigmentdispersion consisting essentially of water, pigment and a dispersingagent, whereby the pigment is impregnated into the porous surface of themembrane.
 13. The colored aluminum or aluminum alloy product of claim 12which is coated with a layer of resin.